The photochemical behaviour of five household pyrethroid insecticides and a synergist as studied by photo-solid-phase microextraction

In the present study, solid-phase microextraction in photochemical studies was used to investigate UV light induced photodegradation of five pyrethroids (empenthrin, transfluthrin, allethrin, phenothrin and cyphenothrin) and a synergist (piperonyl butoxide), which are common ingredients of household insecticides. Gas chromatography coupled with mass spectrometry was used to separate and tentatively identify the parent compounds and their corresponding photoproducts generated in the same polydimethylsiloxane fibre. Kinetics curves were obtained and apparent first-order rate constants and half-lives were estimated. Twenty-six photoproducts were tentatively identified and photodegradation pathways for the compounds investigated were proposed. It is a matter of some concern that three of the photoproducts identified [(3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzaldehyde and (3-phenoxyphenyl)methanol have been reported to be endocrine disruptors. There is no record of previous studies of cyphenothrin and empenthrin photodegradation, and therefore the present study represents the first attempt to elucidate the photochemical behaviour of these compounds.